This invention, which resulted from a contract with the United States Department of Energy, relates to an apparatus for contacting a fluid with particulate material and, more particularly, to an apparatus for contacting nuclear fuel microspheres with processing liquids.
The preparation of gel spheres containing fissile uranium requires efficient contact of the spheres with process liquids. For various reasons it would be advantageous to substitute continuously operating liquid-solid contacting equipment for the batch type apparatus which has been used heretofore for manufacturing such nuclear fuel. However, systems previously designed for aging and washing fuel spheres in a continuous type process have not provided satisfactory liquid-solid contact due to their failure to provide a controlled, efficient counter-current liquid flow which can move the fragile spheres through contact zones without damaging them. Recently, a U-shaped column was tested as a means for continuously contacting fuel spheres with a liquid flowing therein, but it was found that the curved configuration of the lower portion of the column allowed excessive accumulation of spheres therein, making it impossible to maintain constant and continuous sphere movement by manipulation of liquid flow and resulting in damage to the spheres. There is therefore a need for an effective means for contacting fuel spheres with process liquids under controlled counter-current flow conditions.